JPH0696177B2 - Engine valve manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an intake valve and an exhaust valve used in an internal combustion engine, and more particularly to a valve having a larger diameter in a cap portion than a shaft diameter in a valve stem portion. The present invention relates to a manufacturing method effective for molding.

2. Description of the Related Art With the demand for higher engine speed and higher output, engine valves are required to withstand high heat atmosphere and be as light as possible in order to reduce problems with inertia.

As a method of manufacturing an engine valve, there are an electric shrinkage method and a hot extrusion method. In the former method, as shown in Fig. 4, a bar material 1 of heat-resistant steel having the diameter of the stem portion of the engine valve from the beginning is prepared (Fig. 4 (a)), and one end 2 of this material is electrically stretched. After preforming the valve head 3 by deforming it under high temperature and high pressure by the construction method (Fig. 4 (b)), the preformed product is inserted into the die 4 as shown in Fig. 5, and the punch 5 is inserted. Thus, the valve head 3 is hot pressed to form the umbrella portion 6 having a predetermined shape (Fig. 4 (c)). In the latter construction method, as shown in FIGS. 6 and 7, a heat-resistant steel material 7 having a diameter larger than that of a desired stem portion is prepared (FIG. 6 (a)), a die 4'and a punch. This material 7 is subjected to hot front extrusion molding by means of 5'and has a stem portion 8 having a desired shaft diameter at one end.
And a head 3'which is not extruded is left at the other end (Fig. 6 (b)), and this head is hot-pressed by hot pressing with the die 4 and punch 5 of Fig. 5. The umbrella portion 6'having a predetermined shape is formed by pressing (sixth).
Figure (c) figure).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a conventional engine valve molding method, due to various limitations in the electric forging method or the hot extrusion method, the engine valve has a smaller diameter than the stem portion shaft diameter of the engine valve. The diameter of the umbrella part cannot be made large, and to obtain a large lightweight valve for the umbrella part, after forming the umbrella part with a thick material that matches the size of the umbrella part, cut or grind the stem part. Since it is necessary to reduce the diameter to a predetermined value, there is a problem that not only the processing man-hours increase, but also the yield of the material deteriorates.

The object of the present invention is to eliminate the above-mentioned drawbacks and to perform cold axial drawing on the valve stem portion so as to reduce the shaft diameter to a predetermined dimension without cutting or grinding the valve stem portion. An object of the present invention is to provide a method for manufacturing an engine valve that is simple and has a high material yield.

The present invention is to preform a valve head portion at one end and a valve stem portion at the other end of a rod-shaped heat-resistant steel rod material by a hot extrusion method or an electric shrinking method, and then hot press upsetting the valve head portion. In a method of manufacturing an engine valve in which a umbrella portion is formed by molding, a cold shaft drawing process is performed on the valve stem portion to reduce a shaft diameter of the stem portion.

The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing each step of a method for manufacturing an engine valve according to the present invention. The same parts as those in FIG. 4 are designated by the same reference numerals and the same description is omitted. A valve stem 10 having a shaft diameter selected according to the size of the umbrella portion 6 is cold drawn to form a valve stem portion 11 having a reduced shaft diameter. That is, the engine valve having the umbrella portion 6 formed by hot pressing is inserted into the die 12 as shown in FIG.
Thus, the valve stem portion 11 is formed by cold compression from the side of the umbrella portion 6 and axial drawing.

FIG. 2 is a diagram showing each step of the engine manufacturing method according to the present invention. The same parts as those in FIG. 6 are designated by the same reference numerals and the same description is omitted. The preforming of the head portion and the valve stem portion is not limited to the upsetting press by the electric shrinkage method, and may be performed by the hot extrusion press. The valve stem portion 8 thus formed is subjected to cold axial drawing to reduce the diameter of the valve stem portion 11
To form. That is, by hot front extrusion molding, the umbrella 6 '
As shown in Fig. 3, the engine valve with the
Then, the valve stem portion 11 is formed by inserting it into the cylinder 12 and compressing it from the side of the umbrella portion 6'by a punch 13 and cold drawing it.

As is clear from the above description, according to the engine valve manufacturing method of the present invention, after the head or stem portion is preformed by using the steel material having the shaft diameter suitable for forming the umbrella, the valve stem portion is cold-formed. Since the shaft drawing process is performed, it is possible to produce an engine valve that is about 25% larger in umbrella volume than the conventional molding process without shaft cutting process by cutting or grinding. There is also an advantage that the yield of the material is improved.

[Brief description of drawings]

1 (a) to (d) are diagrams showing an example of the construction of an engine valve manufacturing method according to the present invention, and FIGS. 2 (a) to (d) are engine valve manufacturing method according to the present invention. FIG. 3 is a diagram showing the configuration of another example, FIG. 3 is a schematic view showing a punch and die for performing pressing and drawing used for manufacturing the engine valve of the present invention, FIGS. 4 (a) to 4 (c) and FIG. 6 (a) to 6 (c) are diagrams showing a conventional method of manufacturing an engine valve, FIG. 5 is a schematic diagram showing a punch and a die for performing umbrella upsetting, and FIG. 7 is a diagram showing axial extrusion molding. It is the schematic which shows the punch and die which perform. 1, 7 ... Heat resistant steel material, 3, 3 '... Head, 8, 10, 11 ...
… Valve stem part.

Claims (1)

[Claims] 1. A valve head is preliminarily formed on one end of a heat-resistant steel rod material and a valve stem is formed on the other end by a hot extrusion method or an electric shrinking method, and then a hot press is installed on the valve head. A method of manufacturing an engine valve, wherein a valve stem portion is subjected to cold axial drawing to reduce a shaft diameter of the stem portion, in a method of manufacturing an engine valve in which an umbrella portion is formed by ingot molding.